Accurate six-band nearest-neighbor tight-binding model for the π-bands of bulk graphene and graphene nanoribbons

Accurate modeling of the pi-bands of armchair graphene nanoribbons (AGNRs) requires correctly reproducing asymmetries in the bulk graphene bands, as well as providing a realistic model for hydrogen passivation of the edge atoms. The commonly used single-p(z) orbital approach fails on both these counts. To overcome these failures we introduce a nearest-neighbor, three orbital per atom p/d tight-binding model for graphene. The parameters of the model are fit to first-principles density-functional theory -based calculations as well as to those based on the many-body Green's function and screened-exchange formalism, giving excellent agreement with the ab initio AGNR bands. We employ this model to calculate the current-voltage characteristics of an AGNR MOSFET and the conductance of rough-edge AGNRs, finding significant differences versus the single-p(z) model. These results show that an accurate band structure model is essential for predicting the performance of graphene-based nanodevices. (C) 2011 American Institute of Physics. [doi:10.1063/1.3582136]